Coronary dilatation catheters are used to forcibly expand constricted blood vessel areas, particularly the coronary arteries, by means of the pressure of an expanding balloon. Additionally, so-called "bailout perfusion catheters" are also provided to expand and push obstructions outwardly within blood vessels. For example, sometimes the blood vessel wall can collapse inwardly, this condition being called a "dissection". Also, an internal flap of the blood vessel wall may separate and move inwardly. Likewise, blood vessels can constrict due to a vasospasm. Since all of these conditions can result in a severe diminution of blood flow through the blood vessel, they can result in grave clinical injury to the patient unless the situation is remedied by a bailout perfusion catheter, which is inserted to expand the blood vessel again.
In conventional balloon catheters of the above-described type, the amount of time that the balloon can be inflated to forcibly expand the blood vessel is strictly limited, since the expanded balloon may cut off the blood supply more thoroughly than any of the above described conditions that it is attempting to alleviate. Accordingly, one must deflate the balloon, typically after 10 seconds or so of inflation time, whether or not the desired effect has been fully achieved, so that at least some blood flow can take place through the blood vessel being treated.
In Sahota U.S. Pat. No. 4,581,017 a balloon catheter is provided in which auxiliary blood flow paths flow past the balloon while the balloon is in inflated condition within a blood vessel. Thus, blood can be supplied to areas downstream of the balloon inflation through the blood vessel while the balloon remains inflated. However, the flow volume of blood that can be passed downstream is relatively small.
There remains a need for a perfusion or dilatation catheter, which can be used for dilatation in the addressing of blood vessel problems such a dissections, projecting tissue flaps, stenoses, or vasospasms, in which internal dilatation of a blood vessel can be provided while relatively high volumes of blood pass through the area of dilatation. In the Sahota patent it is apparent that only relatively small quantities of blood can pass through the dilatation area.
Also, a simplified catheter is provided by this invention which is capable of exerting a focused, somewhat asymmetrical lateral pressure on a portion of a blood vessel wall, to help reseat a tissue flap or the like during the dilatation procedure.